This is the classic "Knight Tour" Problem. I have used x_mov[] and y_mov[] to define the next co-ordinates the knight will take. The problem is, when I rearrange the arrays x_mov[] and y_mov[] (simultaneously), the program doesn't give an output and results in TLE. But when the order is in a direction from 0 degree to 360 degree, the output is correct.
static int N = 8;
public static void main(String args[]){
solveKTP();
}
static void solveKTP(){
int sol[][] = new int[N][N];
for(int i=0;i<N;i++)
for(int j=0; j<N;j ++)
sol[i][j] = -1;
sol[0][0] = 0;
//This ORDER Does not give the result
//int x_mov[] = {2, 2,-2,-2, 1,-1, 1,-1};
//int y_mov[] = {1,-1, 1,-1, 2, 2,-2,-2};
//This Order GIVES the correct result
//Notice how the direction changes from 1st to 2nd to 3rd to 4th quadrant.
int x_mov[] = {2, 1,-1,-2, -2, -1, 1, 2};
int y_mov[] = {1, 2, 2, 1, -1, -2,-2,-1};
if(backtrack(0,0,sol,x_mov,y_mov,1))
printSol(sol);
else
System.out.println("Not Possible");
}
static boolean backtrack(int x ,int y, int sol[][], int x_mov[], int y_mov[], int movi){
if(movi == N*N) {
//System.out.println("Here");
return true;
}
for( int k = 0; k<8; k++){
int next_x = x + x_mov[k];
int next_y = y + y_mov[k];
if(isSafe(next_x,next_y, sol)){
sol[next_x][next_y] = movi;
if(backtrack(next_x,next_y, sol, x_mov, y_mov,movi+1))
return true;
else
sol[next_x][next_y] = -1;
}
}
return false;
}
static boolean isSafe(int x, int y, int sol[][]){
return (x>=0 && x<N && y>=0 && y<N && sol[x][y]==-1);
}
static void printSol(int sol[][]){
for(int i = 0; i < N; i++){
for(int j = 0; j< N ; j++)
System.out.print(sol[i][j]+ " ");
System.out.println();
}
}
I have searched for the answer but couldn't find it. I'll be grateful if anybody could explain me why is that happening. Please comment is you need any further information.
